Central European Forests Research Articles

Eurasian woodcock (Scolopax rusticola) in intensively managed Central European forests use large home ranges with diverse habitats

Modern management of Europe's forests should strive for a delicate balance between efficient production, which is their primary purpose, and forest management practices that conserve and support biodiversity. This requires detailed knowledge of the ecology of forest-dwelling species, including their site-specific behavior and habitat preferences. One such species is the Eurasian woodcock (Scolopax rusticola), an important game bird that breeds throughout the Palearctic region. Despite its importance, our knowledge of woodcock ecology is limited, and collecting reliable data is challenging due to the species' cryptic behavior. Here, we used high-precision GPS-GSM telemetry to determine home range size and to investigate habitat selection in male Eurasian woodcocks inhabiting Central European forests. Using Bayesian mixed-effects models corrected for spatial autocorrelation, we compared several habitat characteristics (including dominant tree and herb species) of sites where woodcocks occurred with randomly selected sites within their home ranges. Our results show that woodcock in Central Europe move over much larger home ranges during the breeding season (median 7.26 km2) than previously reported in other parts of their breeding range, although they regularly use only small part of this large area (median 1.09 km2). Within their home range, woodcocks used a wide range of habitats, including intensively managed conifer monocultures, but preferred deciduous forests, particularly those dominated by European white birch (Betula pendula). Specifically, 24 % of the plots with woodcock were dominated by birch, compared to only 12 % of the randomly selected plots. Importantly, regardless of dominant tree species, woodcocks preferred sites with dense vegetation cover, but good terrain traversability. During the day, woodcocks preferred sites with dense canopy cover, while at night they preferred more open areas.However, in contrast to previously published results elsewhere, these open areas were more likely to be sparse forest (73%) than grasslands or non-forest cropland (24%), and were characterized by less continuous canopy cover, with a median of only 40%.Our study highlights the importance of specific microhabitats, such as sites with dominant representation of commercially non-target broadleaved species (birch), or sites with sparse canopy cover but denser understorey vegetation. Appropriate management practices that promote such specific microhabitats would have a positive impact on populations of woodcock and other forest species inhabiting commercial forests in Central Europe.

Key structural factors and their thresholds for promoting bird diversity in spruce-dominated production forests of central Europe

Many of native forests in Europe have been transformed into even-aged production forests of commercially attractive conifers. In recent decades, a moderate shift back to a more native tree species composition accompanied by the maturation of some close natural stands has been evident in the Czech Republic. We aimed to investigate the effects of increasing age and contribution of native tree species on bird species and to identify the potential critical thresholds of these factors in central European forests. For this purpose, bird monitoring and forest structure measurements were carried out at 120 plots in production forests and 20 forest reserves located on 20 study sites throughout the Czech Republic. These plots covered gradients of native tree species contribution and stand age. Birds were counted during the 2018, 2019 and 2020 breeding seasons using passive acoustic monitoring, followed by subsequent computer analysis of the recordings. We assessed relationships between differences in bird species composition and structural and environmental factors. We also used generalised additive models (GAMs) to investigate the effects of individual structural and environmental factors on birds, taking into account their occurrence frequencies and habitat preferences. Our results convincingly documented, that dissimilarities in bird species composition, especially species turnover, strongly coincided with differences in the share of conifer basal area and stand age. The effect of tree species composition on the bird species turnover reflected the habitat preferences of individual species. In addition, we found that some cavity-nesting species were strictly associated with stands with a low contribution of conifers and high stand age. The presence of forest older than at least 125, but sometimes up to 280 years is a critical factor for rare and old-growth bird species. Conversely, the high contribution of conifers (more than app. 60 % of basal area) inhibited the occurrence of the species-rich communities, especially the birds associated with close natural stands. Therefore, increasing the area of mature close-natural stands would be beneficial for bird diversity, especially for rare species. In central Europe, however, the rotation length of forest stands is usually less than 120 years in order to maximise timber production. Forest management practices should therefore support the maturation of forest stands and the transformation of tree species composition towards more native broadleaved forest stands. These measures are essential for the protection of species-rich bird communities, especially old-growth-associated birds, in central Europe.

Climate change accelerates ecosystem restoration in the mountain forests of Central Europe

Abstract Restoring degraded forest ecosystems is an important element in the ongoing challenge to sustain the integrity and functioning of the biosphere. However, the evaluation of restoration success is hampered by long lead times of management measures in forests. Moreover, forest change is accelerating also in the absence of management because of ongoing climate change. Yet, because a counterfactual is frequently missing, it remains unclear whether restoration measures are aided or impeded by climate change. Here, we analysed the pace and success of forest restoration under climate change, combining field data and simulation modelling. We focused on the management zone of Berchtesgaden National Park (BGNP), Germany, where restoration aims to restore homogeneous Norway spruce (Picea abies) forests to structurally diverse mixed mountain forests. We evaluated three alternative restoration strategies: Two active strategies focused on planting the currently underrepresented silver fir (Abies alba) and European beech (Fagus sylvatica) but differing in the creation of gap‐cuts, and a third passive restoration strategy without interventions. Strategies were simulated with the forest landscape model iLand from 2020 to 2100 under different climate scenarios (historic, RCP 2.6, 4.5, and 8.5). The forests of BGNP developed into structurally diverse and mixed forests under all evaluated management strategies, and differences between active and passive restoration were generally small. While restoration goals for forest structure were largely met by 2100, forest composition remained far from target in all strategies. Climate change aided restoration by significantly increasing the prevalence of silver fir and European beech (+104.2% to +258.6%). Field data on short‐term restoration effects were in line with simulated long‐term trajectories. Synthesis and applications: We here show that forest restoration efforts in Central European mountain forests will likely be accelerated by climate change. Nonetheless, the slow pace of restoration underscores the need for taking action. Our study highlights that active restoration measures such as tree planting can bring the system closer to restoration targets. However, it also demonstrates that passive restoration (no intervention) is a viable option for management, highlighting the need to evaluate restoration measures against the counterfactual of a no intervention strategy.

Ecophysiological Behavior of Fagus sylvatica L. Growing at Its Southern Distribution Limit: Insights for Understanding the Fate of the European Beech under Warmer and Dryer Growth Conditions

In the last 20 years, a significant mortality of Fagus sylvatica L. (European beech) has been documented in central and northern European forests. Surprisingly, no beech die off occurred at the southern limit. This fact leads us to hypothesize that European beech populations growing at the southern limit of the distribution might have a significant phenotypic plasticity to better cope with low water availability and rising temperatures. To check this hypothesis, we evaluated the ecophysiological behavior of F. sylvatica growing along an altitudinal transect in Calabria (Italy). We selected three study sites (750 m a.s.l., 976 m a.sl. m a.s.l., 1450 m a.s.l.) showing narrow ranges of temperature, rainfall and air humidity. Trees growing at 976 m a.s.l. showed the highest stomatal conductance values during the entire experimental period. The lowest gas exchange and highest leaf mass area were recorded in plants growing at 750 m a.s.l. In the European beech growing at 1450 m a.s.l., higher vessel density, lower mean vessel diameter and higher vessel grouping index values were recorded. Overall, our results highlighted that the measured populations show a considerable phenotypic plasticity leading them to adjust anatomical and physiological traits in response to narrow ranges of environmental parameters. Despite that, the distribution of F. sylvatica seems to be limited to areas with a growing season rainfall of at least 400 mm and vapor pressure deficit (VPD) values < 3 kPa, which may represent the main environmental thresholds which strongly limit the beech growth and, therefore, influence the ability of this species to cope with future environmental conditions.

Intercomparison of recent microwave satellite soil moisture products on European ecoregions

Several satellite microwave-based soil moisture (SM) products have become available in recent years, making possible to produce different datasets at continental and/or a global scale. Numerous variables, including geographic heterogeneity, weather and climate, and land cover, have an impact on these products' accuracy. In this study, we account for all these variables by using the ecoregions as the scale of analysis and conducting a thorough comparison of satellite products with ground-based SM measurements. The whole Europe has been selected as study area, considering it as the aggregation of several ecoregions, each of them classified as an homogeneous zones, in terms of climate, vegetation and potentially investigable soil cover. Selected SM satellite data includes: i) the National Aeronautics and Space Administration (NASA) SMAP L4 V5; ii) the European Space Agency (ESA) SMOS-IC V2.0; iii) the H115 and H116 SM products in time-series format generated by analyzing data collected by the Advanced Scatterometer (ASCAT) aboard MetOp satellites; iv) the CGLS SSM 1 km obtained by the radar onboard ESA’s SENTINEL-1 platforms; and v) the European Space Agency’s Climate Change Initiative for Soil Moisture (ESA CCI SM) “COMBINED” ESA CCI SM v06.1 product, created by merging satellite-based passive/active microwave measurements. Such a variety, in terms of technologies and main features, of publicly available online SM products (in their up-to-date version), allowed for a comprehensive intercomparison against in situ measurements of the International Soil Moisture Network (ISMN), that spreads across all of Europe within the above-mentioned terrestrial ecoregion, using four different metrics, i.e., r, bias, ubRMSE and r/rANOM.Overall the intercomparison has underlined how SMAP L4 and ESA CCI show the best performance regardless of the considered metric. ASCAT has achieved best performances among non-modeled/blended products, while SMOS-IC has showed slightly better performance than the CGLS SSM 1 km. Using ecoregions allowed to further characterize the differences of each satellite products and identify the areas where all these products are more reliable (e.g., group (1) made by ecoregions as the Cantabrian Mixed forests or the Balkan Mixed forests; or group 2 made by ecoregions which belong to Mediterranean area) or less performing (e.g., the Central European mixed forests and the Pontic steppe). Hence, these classes have been further analyzed exploiting the ERA5-Land data, in terms of the SM, air temperature, precipitation, evaporation and Leaf area index. The research has provided helpful insights into how the performance of particular SM satellite products changes based on both the characteristics of the product under consideration and the area under investigation (i.e., one ecoregion compared to another).

Hydrological regime and forest development have indirect effects on soil fauna feeding activity in Central European hardwood floodplain forests

Soil fauna act as regulators of decomposition processes via their feeding activity, thereby playing an important role in regulating carbon cycling and sequestration. Hardwood floodplain forests are critically endangered habitats, but strongly contribute to carbon sequestration in Central Europe. In the present study, within a floodplain forest-development programme, we investigated the feeding activity of soil fauna via the Bait Lamina test in hardwood floodplain forests of the middle Elbe River in Germany in sites with different hydrological regimes and forest-development stages, with neighbouring grassland sites for comparison. While statistically significant differences in overall feeding activity between general hydrological regimes or forest development stages were not found, decreases in feeding activity with soil depth were strongly modulated by these factors, indicating more unfavourable conditions for soil fauna at increasing soil depth due to, e.g., anoxic conditions in floodplains of tributaries or low soil moisture content below the shallow rooting zone of grasslands. Registered effects of soil texture on soil fauna feeding activity were dependent on forest-tree density, and combined effects indicate that soil-fauna feeding activity varies with soil temperature during spring, but with soil moisture in early autumn. In conclusion, our results highlight the importance of the current abiotic conditions on soil-fauna feeding activities in floodplain forests, i.e. soil temperature, moisture and ground water level. Hydrological regime and forest development have a strong impact on the effect of these conditions, indirectly affecting soil fauna feeding activity and highlighting the multifactorial influence on soil fauna functional activity to be considered in floodplain-forest restoration programs.

Why is the hermit beetle so rare in Central European managed forests? Habitat requirements of the forest population of Osmoderma barnabita

In Europe, more than 95% of forests are managed and only 2.2% of forests are undisturbed by man. Therefore, appropriate forest management strategies are crucial to the survival of all forest-dwelling species. Among them are saproxylic beetles, one of the most sensitive to forest management organisms, often treated as important indicators of the degree of transformation of forest ecosystems. The object of our study was the hermit beetle Osmoderma barnabita, so-called primeval forest relict, used as an umbrella species for forest conservation in Central Europe. However, most studies of habitat preferences of this species have been conducted in anthropogenic habitats, and it is not known to what extent they correspond to the habitat requirements of forest populations. The aim of this research was to fill this knowledge gap, as well as to assess differences in characteristics of hollow trees preferred by the hermit beetle between managed and unmanaged forests. Our results indicate that five predictors affect the occurrence of O. barnabita in Central European forests: trunk diameter, tree health, number of entrance holes per tree, size of the entrance hole, and their height above ground, all having positive effect on its presence. The most important predictors were tree health, size of the entrance hole and their height above the ground, while trunk diameter was the least informative variable. Managed and unmanaged forests differed significantly in three out of five characteristics of hollow trees preferred by the species. Unmanaged forests had a greater share of trees with higher trunk diameter, larger hole entrances and poorer health. Therefore, the protection of the species should be based not only on the preservation of hollow trees, but also on maintaining their diversity, ensuring availability of optimal conditions for the local habitat.

Long-term temporal analysis of fatal and severe occupational accidents in Central European forests of the Slovak Republic

Introduction: Forestry is one of the most dangerous industries worldwide. Workers handle heavy loads and are exposed to numerous adverse factors of the work environment. This study was focused on analyzing severe and fatal occupational accidents over a long period. Methods: Data were gathered from occupational safety and health databases of the State Forests of the Slovak Republic, which manages 879,113 ha of forests in Slovakia. Between 2007 and 2021, 210 severe and64 fatal accidents were recorded. The data analyses included contingency tables, Pearson χ2 test, and Cramer’s V coefficient to analyze the relationships between studied variables. Results: The mean annual number of fatalities was 14, occurring to workers aged 42 on average. Almost 80% of all fatal accidents were suffered by contractors of harvesting operations, who were 5.23 times more likely to suffer a fatality than company employees. On average, 1.28 severe and0.75 fatal accidents occurred per 1 million m3 of harvested timber. The outcomes of the correlation analysis showed a decreasing trend in incidence in the case of severe accidents. Workers ≤ 30 years or between 51 and 60 years of age were the most vulnerable in the case of fatal accidents. In the case of severe accidents, workers between 51 and 60 were the most vulnerable group. Most fatal accidents were suffered by tree fellers (72.2%) during felling (69.8%), who were in contact with falling trees and tree parts (93.7% share for this material agent). Conclusion and Practical Applications: The presented study identified the most vulnerable worker groups as well as the effects of factors on the occurrence of severe and fatal occupational accidents in forestry. The results will serve in development of occupational safety and health strategies in forest enterprises.

Norway spruce susceptibility to bark beetles is associated with increased canopy surface temperature in a year prior disturbance

Forest pest infestation is a major driver of tree mortality, altering ecosystem functioning, changing microclimates, and causing significant woodland loss globally. We examined environmental effects on Picea abies susceptibility to bark beetle Ips typographus before and during a multi-year severe outbreak in a protected, natural, Norway spruce-dominated mountain forest in Central Europe. In contrast to recent publications that focus on identifying spectral signatures related to the early (“green”) beetle attack stage, we investigated large-scale signals indicating the predisposition of stands to herbivore infestation in the year preceding the outbreak, using remotely sensed (RS) climate and ecological data. Through partial least square regression, we analyzed interactions between microclimate variables related to susceptible, infested, and healthy spruce stands. Using RS classification maps, we reconstructed the annual forest area changes from 1985 to2020 and linked it to previous climate events.Our findings indicate that the surface temperature in stands subsequently attacked was higher compared to intact stands in the year prior colonization. Over the research period, the forest’s original cover decreased by 50%, with an average annual change of 1.5%. The recorded episodes of above-average tree mortality were linked to extended summer warming and short-term winter temperature declines, accompanied by windstorms. We argue that the use of remotely sensed temperature data can aid in predicting landscape scale spruce susceptibility to bark beetle outbreak one year before the actual attack occurs. This prediction could substantially improve management of forest disturbance, by providing more time to implement preventive or protective measures.

Shifts in intra-annual growth dynamics drive a decline in productivity of temperate trees in Central European forest under warmer climate

Climate change shifts tree growth phenology and dynamics in temperate forests. However, there is still little information on how warming climate changes intra-annual growth patterns and how these changes affect the productivity and carbon uptake of temperate trees. To address this knowledge gap, we used high-precision growth data from automatic dendrometers to quantify the impacts of unusually warm weather in 2022 (hot year) on growth phenology, dynamics and aboveground biomass (AGB) production in eight common temperate species (both conifers and broadleaved) in the Czech Republic. Mixed-effect models were used to investigate inter-annual changes in the start, end, and length of the growing season and intra-annual growth dynamics. We also modelled how changes in growth phenology, growth rates, and tree size affected yearly AGB production of individual trees. In the hot year, the growth started 5 days earlier, peaked 22 days earlier and ended 20 days earlier than in the climatically normal year, resulting in a shorter growing season with fewer growing days. AGB production decreased 36 % in the hot year, mainly due to fewer growing days and lower maximum growth rates, but with significant variation among tested species. The decline in AGB production in the hot year was most significant in the most productive species, which were also the species with the greatest reduction in the number of growing days. Tree size strongly enhanced AGB production, but its effect did not change with climate variation. Our findings suggest that climate change is likely to advance but also shorten the growing season of temperate trees, resulting in lower biomass production and carbon uptake. The results also indicate that the fast-growing and highly productive temperate tree species will have their growth reduced most by climate change, which will increasingly limit their high carbon sequestration potential.

Use of viscera from hunted roe deer by vertebrate scavengers in summer in central European mountainous mixed forest

Carrion is a valuable resource in forests, providing sustenance for vertebrate and invertebrate scavenger communities and contributing to ecosystem functions, such as nutrient cycling. Intensive ungulate hunting, and thereby extraction of carcasses, removes large quantities of potential carrion from the system, denying a valuable resource from scavenger fauna. It may be possible to reduce the loss and negative consequences to forest biodiversity by retaining evisceration residues from hunted deer, where full carcasses cannot be retained. However, what roll evisceration residues play as a resource for scavengers in temperate forests is not well understood. In this study, we exposed 47 carrion samples from hunted roe deer, in front of triple sets of camera traps, to examine how hunting remains are removed and fed upon by vertebrate scavengers. Overall, 70% of the samples were completely removed from experimental sites by vertebrates. We detected twelve vertebrate taxa feeding on evisceration residues, including martens (Martes spp.), red kites Milvus milvus and garden dormice Eliomys quercinus. Common buzzards Buteo buteo and Eurasian jays Garrulus glandarius were the most frequent feeders on carrion samples, while red foxes Vulpes vulpes displaced the largest proportion of samples. Finally, we found a range of insectivorous bird and mammal species using hunting remains as a source for invertebrate prey, while not scavenging on the remains directly. We demonstrate that evisceration residues can be a valuable resource for a wide range of taxa and suggest that viscera retention from hunted game may contribute to resource provisioning for scavengers in forest ecosystems.

Using a Machine Learning Approach to Classify the Degree of Forest Management

A prerequisite for sustainable forest management is knowing the total diversity and how management affects forests. Both are poorly studied and relate to canopy diversity and comparison with primary forests. From 2001–2004, we fogged beetles from oaks in primary and disturbed, managed sites in Białowieża (Eastern Poland) and also in distant age-class forests. Using a machine learning (ML) method (elastic net), we identified a beetle signature based on the species abundance distribution to distinguish these forest types. The beetle communities from 2001 served as training data, with 21 signature species correctly assigning the oaks to primary and different managed forests. However, the predictive quality of the signature decreased with each year due to high spatio-temporal heterogeneity and beta diversity. To improve the power of the signature, we combined the data from all years to calculate a more general model. Due to its greater complexity, this model identified 60 species that correctly classified both the studied forests and foreign forests in Central Europe, increasing the possibility of a general classification. Further research is needed to determine whether it is possible to establish a general signature-based index on a large number of samples from different years and forest types.

Stabilization of the pine increment during recent years of low precipitation and high temperatures by removal of the spruce lower storey

In stands dominated by Scots pine in Central European nutrient-poor sandy forest sites, deterioration of pine health due to recent development in climate change has been observed, whereas the vitality of the Norway spruce growing in the lower storey of such stands has remained stable. The study aims to analyse the impact of the spruce lower storey on pine increments and performance in relation to drought stress. Wood core samples were collected using an increment borer from mature pines growing in deep, sandy soils with ground water at a depth that was unreachable by the roots in three plot pairs (blocks) consisting of a pine-spruce plot and a plot with the lower-storey spruce removed. The increments of earlywood and latewood were measured separately. Health status and soil moisture were also evaluated. Spruce removal increased the radial growth (tree ring width – TRW) of the pines, and this manifested earlier in the latewood. Spruce removal significantly changed relationship of TRW and umbrothermic index of released pines. The treatment also increased pine foliation, while increases of topsoil moisture in the transects were insignificant. The study indirectly proves the existence of inter-species competition in the rooting zone for water in soils where the ground water is unreachable by the roots. The flat root system of spruce creates a barrier that reduces the amount of water available for pines with deeper growing roots. To reduce the risk of the negative impact of unfavourable climate change on pine as the target species in commercial mature mixed pine forests with similar site and stand conditions, lower-storey spruce reduction can be recommended, even though this might locally and temporarily lessen the biodiversity of the forest stand.

Effects of understory characteristics on browsing patterns of roe deer in central European mountain forests.

Selective browsing by deer on young trees may impede the management goal of increasing forest resilience against climate change and other disturbances. Deer population density is often considered the main driver of browsing impacts on young trees, however, a range of other variables such as food availability also affect this relationship. In this study, we use browsing survey data from 135 research plots to explore patterns of roe deer (Capreolus capreolus) browsing pressure on woody plants in mountainous forests in central Europe. We fitted species-specific generalised linear mixed models for eight woody taxa, assessing the potential effects of understory characteristics, roe deer abundance and lying deadwood on browsing intensity. Our study reveals conspecific and associational effects for woody taxa that are intermediately browsed by roe deer. Selective browsing pressure was mediated by preferences of plants, in that, browsing of strongly preferred woody taxa as for example mountain ash (Sorbus aucuparia) and of least preferred woody taxa, for example Norway spruce (Picea abies) was not affected by the surrounding understory vegetation, while browsing pressure on intermediately browsed species like for example silver fir (Abies alba) was affected by understory characteristics. Contrary to our expectations, roe deer abundance was only positively associated with browsing pressure on silver fir and bilberry (Vaccinium myrtillus), while all other plants were unaffected by deer abundance. Finally, we did not find an influence of lying deadwood volume on the browsing pressure on any woody-plant species. Overall, our results indicate that patterns in browsing preference and intensity are species-specific processes and are partly affected by the surrounding understory vegetation. Current management strategies that aim to reduce browsing pressure through culling may be inefficient as they do not address other drivers of browsing pressure. However, managers also need to consider the characteristics of the local understory vegetation in addition to deer abundance and design species-specific plans to reduce browsing on woody plant taxa.

Intense game grazing shapes epigeic spider communities of pedunculate oak Quercus robur plantations in anthropogenic environments

Game browsing affects nature conservation because the interests of hunters and gamekeepers often lead to high game stocking rates. However, the compositional effects of game browsing on invertebrates are insufficiently understood. We addressed the dynamics of epigeic spider communities in oak stands planted in newly formed anthropogenic environments under the facultative pressure of browsing game. The study site consisted of an open-cast lignite mine and an overburden deposit in NW Czechia. Using pitfall traps, we examined five habitat types (four transects per habitat type): Quercus robur stands ≥ 25 years of age, 12–24 years of age, and 0–2 years of age; Q. robur stands 12–24 years of age that were heavily damaged by game browsing; and sites subject to spontaneous succession for 12–22 years. We captured 9459 individuals from 134 spider species distributed unevenly across the examined habitat types. The young stands were dominated by Pardosa agrestis, Pardosa monticola, and Oedothorax apicatus, whereas Pardosa prativaga, Pardosa lugubris, Pisaura mirabilis, and Alopecosa cuneata dominated the old stands. The stands damaged by browsing had the highest species richness and were dominated by Alopecosa pulverulenta, Xerolycosa miniata, A. cuneata, and Trochosa ruricola. All the oak stands were rich in threatened species, with most (26) found in habitats damaged by browsing, whereas the youngest stands hosted the lowest number of threatened species (11). The species dominating old stands still included species that prefer greater canopy openness, such as P. lugubris, whereas numerous species of central European climax oak forests were lacking. In conclusion, we identified oak stands heavily damaged by game browsing as a unique environment that shapes the community of epigeic spiders and that differs from epigeic spider communities of oak stands of various ages and those colonizing areas that are allowed to undergo spontaneous succession.

Assessing the suitability of under-represented tree species for multifunctional forest management—an example using economic return and biodiversity indicators

Abstract A shifting focus in forest management from timber production to resilience and multifunctionality in the face of changing disturbance regimes might entail altering the species composition of forests. Although the conifers Douglas fir (Pseudotsuga menziesii) and silver fir (Abies alba) currently comprise only a small proportion of Central European forests, the prospect of widespread planting of these species as a climate adaptation measure is currently widely debated by forest managers. To inform this debate, objective assessments of the multifunctional value of these species are required. Here, we introduce Pareto frontiers to objectively assess the value of tree species under competing objectives and considering an uncertain future. Using these frontiers, we explore trade-offs between financial performance and biodiversity aspects of German tree species portfolios with and without these currently rare conifers. We compare several potential biodiversity indicators (related to herbivores, saproxylic beetles, and deadwood decomposition rates) that can be derived from standard forest inventory data. Our results indicate that optimizing the biodiversity indicators generates gradual decreases in financial performance at first, but after an inflection point soil rent declines sharply. Portfolios excluding Douglas fir and silver fir achieved comparable biodiversity levels, but much weaker financial performance, than portfolios that included these conifers. Our novel approach of generating Pareto frontiers that integrate uncertainty can offer useful insights into ecosystem services trade-offs in contexts where risk is unequally distributed across management alternatives.

Quantifying surface fuels for fire modelling in temperate forests using airborne lidar and Sentinel-2: potential and limitations

Surface fuel information is an essential input for models of fire behaviour and fire effects. However, spatially explicit, continuous information on surface fuel loads and fuelbed depth is scarce because the collection of field data is laborious, while suitable methods for deriving estimates from remote sensing data are still at an early stage of development. Fine-scale surface fuel mapping using both passive and active remote sensing has not yet been carried out in Central European forest types, and it remains unexplored how prediction uncertainties of different fuel components affect modelled fire behaviour. This study combines very detailed airborne lidar and multispectral satellite data to extract metrics describing forest structure and composition in two forested areas in southwestern Germany. These metrics were used to predict field-sampled surface fuel components using random forest regression. Accuracies of continuous fuel load predictions were compared to accuracies that could be achieved if only forest type-specific average fuels were assigned. Results revealed that models based on remotely sensed metrics explain part of the variance in litter and fine dead woody fuels (R2=0.27-0.41), but not in coarser dead woody fuels. Estimates for herb and shrub fuels were fairly accurate (R2=0.55-0.64) but limited for the more fire-relevant fine fraction of shrub fuels (R2=0.39). Fuelbed depth was moderately well predicted based on remote sensing data (R2=0.44). Lidar-derived metrics were particularly useful for predicting understory fuels and fuelbed depth. Litter and fine woody fuel predictions were linked to canopy characteristics captured with both lidar and multispectral data and similarly accurate estimates could be obtained using average values based on forest type. We used the fine-scale surface fuel maps derived from remote sensing to predict potential surface fire behaviour in the study area and analysed the sensitivity of modelled fire behaviour to errors in the predicted loads of different surface fuel components: fire behaviour was most sensitive to errors in litter and especially shrub fuel loads, hence estimates of these components need to be improved. Overall, this study showed that statistical relationships between remotely sensed metrics describing forest composition and structure and surface fuels have some potential for estimating fuel loads in Central European forest types and should be further developed to provide starting points for realistic fire behaviour models.

Effects of root plates, pits and mounds following windthrow events on the biodiversity of plants and lichens in Central European mountain forests

Windthrows lead to the formation of a characteristic land microtopography and they provide new habitats and substrata for species. The present study is novel, because it concerns different taxonomic groups of organisms and effects of various variables on species composition, richness and abundance within root plate-pit-mound (RPM) complexes. For the first time we studied lichens, liverworts, mosses and vascular plants on RPM complexes across major vegetation types, from deciduous to coniferous forests. We analyzed 164 RPM complexes which included in total 268 components: 115 root plates, 80 pits and 73 mounds. Besides the vegetation types and component types the following variables were also considered: dimensions (area, size), age (decomposition degree), species of the uprooted tree, shade, and elevation. The research revealed that root plates, pits and mounds had their own indicator species, but the key factors for the species composition were the species of uprooted trees and the vegetation type. Furthermore, the type of component and the vegetation type were also the most main variables determining the richness and abundance of the studied taxonomic groups of species. Analyses revealed the greatest species richness and abundance of lichens on root plates, and the highest richness of liverworts and vascular plants in pits. The type of component had no effect on the species richness of mosses. However, they were most abundant on mounds. The response of individual groups to the vegetation types and other variables varied. Findings from the study indicated that the presence of uprooted trees with different features (size and age, species of uprooted tree) is important for the biodiversity of mountain forests. We recommend leaving uprooted trees in forest communities for natural colonization, preferably large objects. Moreover, in managed forests a mosaic of forest communities that mimic the structure of natural unmanaged forests should be supported.

Leaf litter arthropods show little response to structural retention in a Central European forest

Decomposition of leaf litter is a central process of energy and nutrient cycling in forests, in which arthropods hold important roles. Thus, safeguarding the diversity of organisms including arthropods is increasingly being considered in contemporary forestry, not least to facilitate continued ecosystem functioning. Retention forestry tries to achieve biodiversity conservation by preservation of tree structural elements such as deadwood and tree microhabitats to provide more heterogeneous habitat. Leaf litter arthropods are, however, only indirectly connected with tree structure, which raises the question if and how the currently practised retention forestry influences the leaf litter arthropod community. As the leaf litter arthropod community includes a very diverse range of taxa that is challenging to identify morphologically, we sampled environmental DNA from leaf litter on 66 plots in the Black Forest in southern Germany that were distributed over gradients of forest and landscape features and differed in forest management intensity. We found that the richness of operational taxonomic units, a surrogate for species, was not related to forest structure but tended to increase with recent harvest intensity (which did not exceed a medium harvest intensity on our plots). Community composition was related to the share of coniferous trees present on a plot, and to a lesser extend to elevation and leaf litter coverage. Our results indicate that the leaf litter arthropod community is not responsive towards different degrees of forest structural changes introduced by management as long as the forest type is retained.

Evergreen ivy vines as a key element maintaining the high diversity of birds wintering in Central European forests

Animals face numerous difficulties during winter due to food deficiencies and adverse weather conditions. They are likely especially important in landscapes affected by humans like managed forests, which often have simplified structures that result in a deficiency of arboreal microhabitats crucial for many species. We examined the effects of ivy vines’ presence in Central European upland deciduous forests on bird diversity during winter. We found that forest patches with dense ivy vines on trees strongly attracted wintering birds, which increased the species richness, abundance, and phylogenetic diversity of bird communities. This was true for all plots, regardless if they were located in forest interiors or on the edges. Ivy was the crucial element for bird diversity in forest interiors, whereas in forest edges, veteran trees, dead trees, and bushes also played a substantial role in bird wintering activity. This study demonstrated that lianas (i.e., ivy vines), generally rare elements of temperate forests, are important for the maintenance of forest biodiversity, particularly during the winter periods. Therefore, forest patches with ivy vines should be protected in European forests to enhance overall forest biodiversity.